The present invention relates to a tuner module for a radio receiver, and more particularly, to a tuner module suitable for an in-vehicle digital radio receiver for receiving an electric wave (hereinafter, referred to as “satellite wave”) from a satellite or an electric wave (hereinafter, referred to as “terrestrial wave”) from an earth station to provide digital radio broadcasting.
Recently, a digital radio receiver receiving the satellite wave or the terrestrial wave from the SDARS satellite to provide digital radio broadcasting has been developed and put in practical use in the United States. The digital radio receiver is generally mounted in a mobile object such as an automobile, receives the electric wave in the frequency band of about 2.3 GHz, and provides the radio broadcasting. That is, the digital radio receiver is a radio receiver capable of providing the mobile broadcasting. Since the frequency of the reception electric wave is about 2.3 GHz, the reception wavelength (resonance wavelength) λ at that time is about 128.3 mm. The terrestrial wave is formed in the manner that the satellite wave is received by an earth station, the frequency of the received satellite wave is slightly shifted, and the wave is re-sent in a linearly-polarized wave. That is, the satellite wave is a circular-polarized wave, but the terrestrial wave is the linearly-polarized wave.
Since the electric wave in the frequency band of about 2.3 GHz is used in such digital radio broadcasting, an antenna receiving the electric wave is required to be installed outdoors. Accordingly, when the digital radio receiver is mounted in an automobile, the antenna of the digital radio receiver is required to be installed on the roof of the automobile. Such an automobile antenna and a receiver body (head unit) installed in the interior of the automobile are electrically connected to each other through a cable. The head unit serves as an external device.
A system for receiving this kind of the satellite wave or the terrestrial wave includes an antenna unit (antenna device) and a tuner unit (satellite radio tuner). The antenna unit (antenna device) receives the satellite wave or the terrestrial wave and then outputs a reception signal with high frequency. The tuner unit (satellite radio tuner) demodulates the reception signal and then outputs a sound signal.
Electronic components constituting such a tuner are mounted on a printed circuit board and housed in a metal case as a shield (e.g., see Japanese Patent Publication No. 06-209268A).
A related-art satellite digital radio receiver will be described with reference to FIG. 8. The satellite digital radio receiver includes an antenna 101, a tuner unit 102, a signal demodulating unit 103, a channel demodulating unit 104, a sound decoder 105, a data decoder 106, a control unit 107, and an operation unit 108 (e.g., see Japanese Patent Publication No. 2002-344335).
As described above, the electronic components constituting the tuner are mounted on the printed circuit board. In the printed circuit board, an RF input portion for inputting the reception signal with high frequency (RF) received by the antenna device is formed. There are a first case where the reception signal is inputted to the printed circuit board through a coaxial cable and a second case where the reception signal is inputted to the printed circuit board through an RF connector, in accordance with customer's desire. In the first case, the front end of the coaxial cable is soldered to the RF input portion. In the second case, the front end of the RF connector is directly connected to the RF input portion. To cope with these kinds of cases, in the related-art printed circuit board for a tuner, a pattern of the RF input portion is changed for the first and second cases. In other words, in the related-art printed circuit board for a tuner, there are arranged two kinds: a printed circuit board having an RF input portion for attaching the coaxial cable; and a printed circuit board having an RF input portion for directly attaching the RF connector.
For this reason, in the related-art printed circuit board for a tuner, there are problems that the number of design processes increases, and thus the cost of manufacturing the printed circuit board increases.